This invention is related to control valves of the type used in controls for fluid actuated systems wherein the control valve has a visual indicator of a condition in the system incorporated with the control device. More particularly, this invention is related to a visual indicator for a pilot valve which functions in cooperation with a pressure sensor to maintain fluid pressure to an actuator and release same wherein the visual indicator is mounted on a slide valve of the control valve.
In the prior art several slide valve style fluid actuated control valves are known which function as a pressure sensitive pilot valve or relay and perform some function in a fluid control system. These known control valves do not always provide any positive indication of whether or not operating fluid pressure is present in the system. Furthermore, because some of the prior art valves can be locked temporarily in one position they can, if not fully understood, give a false impression of the condition of a system. Two such control valves of this nature are shown in U.S. Pat. Nos. 3,943,974 and 3,823,739. In a system employing adequate and substantial safety measures it is common to include auxiliary indicators at various points in the system to indicate the presence of or the absence of adequate operating fluid pressure in the system. For a system using the above described, indicating devices must be used to provide a clear and accurate indication of conditions in the system. While a system using this style of control valves can function adequately, it has several disadvantages. One major disadvantage in this type of system is that many additional components are needed which increase the possibilities of failure in the system as well as the expense of making same. Other disadvantages of using separate indicators become apparent upon detailed examination of a specific system and considering, mounting, placement, repair, dependability and operator access to the auxiliary indicators and the control valves. In considering shortcomings of the prior art devices, it is worthwhile to note that many prior art slide type control valves are not structurally designed to be combined with an indicator in a single integral unit.